<template >
  <div class="pagination">

    <button :disabled='pageNo == 1'
            @click="$emit('getPageNo',pageNo-1)">上一页</button>

    <button v-if="pageNo > 3"
            @click="$emit('getPageNo',1)"
            :class="{ active: pageNo == 1 }">1</button>

    <button v-if="pageNo > 4">···</button>

    <button v-for='(page,index) in startNumAndEndNum.endNum'
            :key="index"
            v-if="page>startNumAndEndNum.startNum-1"
            @click="$emit('getPageNo',page)"
            :class="{ active: pageNo == page}">{{page}}</button>

    <button v-if="startNumAndEndNum.endNum < totalPage-1">···</button>
    <button v-if="pageNo < totalPage-3"
            @click="$emit('getPageNo',totalPage)"
            :class="{ active: pageNo == totalPage}">{{totalPage}}</button>

    <button :disabled='pageNo==totalPage'
            @click="$emit('getPageNo',pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共{{total}}条</button>
  </div>
</template>
<script>
export default {
  name: "Pagination",
  props: ['pageNo', 'pageSize', 'total', 'totalPage', 'continues'],
  computed: {
    startNumAndEndNum () {
      //起始数字和结束数字
      let startNum = 0, endNum = 0
      //解构数据 方便使用
      const { pageNo, pageSize, total, continues, totalPage } = this
      if (total < continues) {
        startNum = 1
        endNum = totalPage
      } else {
        //parseInt取整
        startNum = pageNo - parseInt(pageSize / 2)
        endNum = pageNo + parseInt(pageSize / 2)

        if (startNum < 1) {
          startNum = 1
          endNum = continues
        }
        if (endNum > totalPage) {
          startNum = totalPage - continues
          endNum = totalPage
        }
      }
      return { startNum, endNum }
    }
  }
}
</script>
<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  background: skyblue;
}
</style>